Nonlinear Performance of Reinforced Concrete Frame with Infill Wall

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Nonlinear Performance of Reinforced Concrete Frame with Infill Wall Pranav Dhumal1, Prof. R.M. Desai2 1M.

Tech Structural Engineering (student), Sanjay Ghodawat University, Kolhapur.

Civil Engineering Department, Sanjay Ghodawat University, Kolhapur.

---------------------------------------------------------------------***---------------------------------------------------------------------2Professor,

Abstract - The influence of the infill wall on the global reaction of the RC structures cannot be overlooked, as evidenced by historical earthquakes and experimental testing conducted since the mid-1950s. As a result, the seismic susceptibility of these types of structures must be examined by taking into account the infill wall's influence in order to establish their degree of safety and, as a result, to identify any prospective reinforcing requirements. The non-linear analysis of the building is the subject of this study. Fully infilled and infilled with open ground floor constructions were chosen, and their behavior was compared to that of the comparable bare frames. A single strut model with characteristics calibrated using experimental data was used to mimic the behavior of the infill panel.

brick infill masonry (model-2), and 10 storey RC frame with brick infill masonry having open ground storey i.e. no infills at ground level (model-3). Elevation of all three models are presented in fig 1. Response Spectra Considered -IS 18932016, Seismic zone – IV, Seismic, zone factor Z = 0.24 Importance factor I = 1, Soil type = I, Response Reduction factor = 5. The loads considered are Floor finish = 1.2 KN/Sqm. Floor finish (roof) = 1.5 KN/Sqm. Live load = 3 KN/Sqm. Live load (Roof) = 1.5 KN/Sqm. Wall load = 12 KN/m. The dimension of beam and column are listed in table-1 and table-2.

Key Words: Sap2000, modelling of infill wall, nonlinear static analysis, FEMA-356.

1.INTRODUCTION Clay brick is a common form of material used in the world's construction industry for the construction of reinforced concrete (RC) structures' walls. Brick masonry has a high mass and accounts for 30-35 percent of the total mass of the structure. The brittle quality of brick masonry infill (BMI) makes it strong in compression. In-plane stiffness is high, whereas out-of-plane stiffness is low. Because these are particularly stiff in nature, they attract bigger seismic pressures and fail first during an earthquake.

Asymmetrically placed BMI, leads to seismic torsion since the mass of the BMI is also asymmetrically positioned. This could be for aesthetic reasons or due to the provision of apertures. To asses the influence of brick infill, a non-linear approach is required which shows particular damage state.

Model – 1

Model – 2

Model – 3

Fig- 1: Elevation of RC frame with and without infill Table-1 Schedule of Beam Beam Title

Size mm

in

B1

450 300 450 300

x

B2

x

Main steel At At top bottom 4-16 4-16 Ф Ф 3-16 4-16 Ф Ф

Remark Up to storey 5 Storey 6 to 10

2. Structural Modelling Table-2 Schedule of Column

A 10 storey R.C. framed structure 16m x16m in plan (Model1) is selected for development of fragility curves. Since the example building is a new building, first a linear dynamic analysis is performed for determination of forces and moments in various frame elements and then it is designed for various load combinations specified in the IS-2000 and IS-1893.2016 code for member optimizations. To introduce the effect of brick masonry infill, an equivalent diagonal strut is assigned in model-1 as explained IS-1893-2016.

Properties required to design diagonal strut for brick infill masonry 1:3, are taken from Kaushik et al (2007). To introduce the effect of soft storey all the infill struts of ground storey were removed. 10 storey RC frame without brick infill masonry (model-1), 10 storey RC frame with

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Column Title

Size in mm

Main steel

Remark

C1

500 x 500

14-25 Ф

C2

450 x 450

12-20 Ф

Up to storey 3 Storey 3 to 6

C3

450 x 450

8-16 Ф

Storey7 to 8

C4

400 x 400

8-16 Ф

Storey 9 to 10

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International Research Journal of Engineering and Technology (IRJET)

e-ISSN: 2395-0056

Volume: 09 Issue: 02 | Feb 2022

p-ISSN: 2395-0072

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2.1 Non-linear modelling of structure The plastic hinges are based on the default hinge model which is defined in SAP2000. For beam section, the moment M3 hinge type was used as well as the column section, which is the Interacting P-M2-M3. Geometric nonlinearity has been considered by incorporating P-∆ effect in the analysis. For non-linear modelling of equivalent diagonal strut axial deformation (ductile) hinge is assigned.

3. Pushover Analysis Pushover analysis (POA) was carried out on all three models.

In this analysis, lateral load applied plays an important role in evaluating the structure performance according to the pushover analysis. In this analysis, as suggested in FEMA356, A uniform lateral load was applied to perform the analysis. POA was performed by incrementally increasing the magnitude of lateral load and analyzed using SAP2000v21 software. Based on the results of this analysis, the capacity curve managed to be developed. The percentage of drift was calculated. In this study, the percentage of drift is limited to 4% as suggested in FEMA-356.

(c) Fig. 2 Capacity Curve (a) model-1,(b) model-2,(c) model-3 As per the performance levels suggested in FEMA-356, the performance of the three model is listed in table-3.

Table-3: Performance level- FEMA 356 Model-1 Drift %

Model-2 Drift %

Model-3

IO

1

Base Shear KN 7561

Drift %

1

Base Shear KN 19136

1

Base Shear KN 12126

LS

2

11110

2

18432

2

12572

CP

4

11345

4

10983

4

11390

4. Plastic hinges

(a)

(a)

(b)

(c)

Fig.3 Plastic hinge formation at Drift 4% (a) model-1, (b) model-2,(c) model-3 (b)

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Figure-3 shows the plastic hinge pattern when the structure is pushed to 4% drift. In model three a soft storey mechanism is observed.

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3. CONCLUSIONS

[6]

FEMA 356. Prestandard and Commentary for the Seismic Rehabilitation of Buildings. Building Seismic Safety Council (US), and Applied Technology Council, Redwood City, California; 2000.

[7]

BIS. IS 1893 (Part 1): 2016, Criteria for Earthquake Resistant Design of Structures: Part 1 General Provisions and Buildings. In: 6th Rev., Bureau of Indian Standards, New Delhi, India.

[8]

H. Krawinkler, G.D.P.K. Seneviratna, Pros and cons of a pushover analysis of seismic performance evaluation, Eng. Struct. 20 (4–6) (1998) 452–464, https:// doi.org/10.1016/S0141-0296(97)00092-8.

[9]

Structural analysis program (SAP2000). Advanced, static and dynamic finite element analysis of structures, Computers and Structures, Inc., Berkeley, Calif., 2004

After performing non-linear static analysis for three models a capacity curve is derived which gives idea about behavior of structures under lateral loading.

1. According to the graph, maximum base shear for bare frame is 11775 KN at the drift of 2.97%, Infill frame is 19564 KN at the drift of 1.47% and for open ground storey is 12592 KN at the drift of 2.31%. which shows that masonry infill increases the stiffness of structure and resist more lateral load.

2.

As performance levels defined in FEMA-356 for IO, LS and CP are marked on capacity curve for 1%, 2% and 4% drift. Value of base shear drops after LS i.e 2% drift for brick masonry infill frame, which is due to failure of infill masonry, whereas for bare frame the curve is smooth and value of base shear is constantly increasing.

3. In open ground storey. A soft storey mechanism is observed in this model. The columns of these storey are failed due to change stiffness.

4.

values of base shear for Bare frame are in increasing order whereas for infill and open ground storey, base shar drops after 2% drift. Due to failure of infill masonry.

REFERENCES [1]

ATC-40, “seismic evaluation and retrofit of concrete building”-volume I, Report no. SSC 96- 01, Redwood City, Applied Technology Council, 1996

[2]

Murty CVR, Rai DC, Jain SK, Kaushik HB, Mondal G, Dash SR. Performance of structures in the Andaman and Nicobar Islands (India) during the December 2004 Great Sumatra earthquake and Indian Ocean tsunami.

Earthquake Spectra, 22(S3), EERI, USA, Special Issue June 2006; 2006. p. S321–54.

[3]

Kaushik HB, Jain SK. Impact of great December 26, 2004 Sumatra earthquake and tsunami on structures in Port Blair. J Perform Constr Facil, ASCE 2007;21(2):128–42.

[4]

Kaushik HB, Rai DC, Jain SK. Effectiveness of some strengthening options for masonry-infilled RC frames with open first storey. J Struct Eng, ASCE 2009;135(8):925–37.M. Young, The Technical Writer’s Handbook. Mill Valley, CA: University Science, 1989.

[5]

Basha SH, Kaushik HB. Behavior and Failure Mechanisms of Masonry-Infilled RC Frames (in Low-Rise Buildings) subject to Lateral Loading. Eng Struct 2016;111(15):233–45. Elsevier https://doi.org/10.1016/j.engstruct.2015.12.034.

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